In a power transmitting apparatus transmitting engine power of a vehicle, such as an automobile, to its wheels, it is necessary not only to transmit the power from the engine to the wheels, but also to allow for radial and axial displacements. Moment displacement from the wheels is caused by bounds or turns of the vehicle during running on rough roads. One end of a drive shaft, arranged between an engine side and a driving wheel side, is connected to a differential gear unit via a constant velocity universal joint of the sliding type. The other end of the drive shaft is connected to a driving wheel via a wheel bearing apparatus including a constant velocity universal joint of a secured type.
Various types of wheel bearing apparatus have been previously proposed, for example, as shown in FIG. 8. The wheel bearing apparatus 50 includes a wheel hub 51 having a wheel W and a brake rotor B mounted to it. A double row rolling bearing 52 rotationally supports the wheel hub 51. A secured type constant velocity universal joint 53, for transmitting power from a drive driving shaft (not shown in figure), is connected with the wheel hub 51.
The wheel hub 51 is integrally formed with a wheel mounting flange 54 at one end. The wheel mounting flange 54 mounts the wheel W and the brake rotor B. A cylindrical portion 51a axially extends from the wheel mounting flange 54.
The double row rolling bearing 52 is formed with a double row angular contact ball bearing. An outer ring 55 is mounted between a knuckle N, forming part of the suspension apparatus and the cylindrical portion 51a of the wheel hub 51. The outer ring inner circumference includes double row outer raceway surfaces 55a, 55a. A pair of inner rings 56, 56 is arranged opposite to the double row outer raceway surfaces 55a, 55a. Each inner ring 56, 56 is formed on its outer circumferences with an inner raceway surface 56a, 56a. Double row balls 58, 58 are rollably contained, via cages, 57 between the inner and outer raceway surfaces 55a, 55a and 56a, 56a. 
The constant velocity universal joint 53 has an outer joint member 61 with a cup shaped mouth portion (not shown). A shoulder 59 is formed at a bottom of the mouth portion. A shaft portion 60 axially extends from the shoulder 59. The outer joint member 61 is inserted into the wheel hub 51, via a serration, in a torque transmittable fashion. The shaft portion 60 is inserted into the wheel hub 51 until the shoulder 59 abuts against the inner ring 56 of the double row rolling bearing 52. A securing nut 63 is fastened onto an outer thread 62, formed on one end of the shaft portion 60, by a predetermined fastening torque to axially separably connect the wheel hub 51 and the outer joint member 61.
It is known that a large torque is transmitted to the wheel W via a sliding type constant velocity universal joint (not shown) from an engine during a low engine speed range, such as in starting of a vehicle. Thus, a torsional force is caused in the driving shaft. As a result, a torsional force is also caused in the inner ring 56 of the double row rolling bearing 52 that supports the driving shaft. When a large torsional force is caused in the drive shaft, a so-called “stick-slip noise” is generated due to a sudden slippage caused between abutting surfaces of the shoulder 59 of the outer joint member 61 and end face of the inner ring 56.
To cope with this problem in the prior art wheel bearing apparatus 50, a surface machining, to reduce a frictional resistance, is made on a part abutting against the shoulder 59 of the outer joint member 61. More particularly, as shown in FIGS. 9(a) and (b), grooves 64, for receiving grease, are circumferentially formed along the end faces 56b, 56c of the inner ring 56. These grooves 64 help the introduction of grease into an interface between mutually adjacent surfaces. Thus, this reduces the frictional resistance. Accordingly a smooth slippage can be caused therebetween and thus the generation of the stick-slip noise can be suppressed. See, Japanese Laid-open Patent Publication No. 110840/2000.
However these surface machinings made in plural parts increase the machining steps and complicate the process management. Thus, this prevents a reduction of the manufacturing cost.
Additionally, in the prior art wheel bearing apparatus, the securing nut 63 is fastened to the outer thread 62 of the shaft portion 60 of the outer joint member 61. A fastening force (axial force) exceeding a predetermined level is required to adjust and control an amount of pre-pressure of the double row rolling bearing 52. Although it is possible to reduce the frictional resistance at first by grease applied between the abutting interfaces, a risk arises in that the applied grease would be forced out by the fastening force. Thus, it is difficult to keep the friction reducing effect for a long term.